title: A novel anticonvulsant modulates voltage-gated sodium channel inactivation and prevents kindling-induced seizures.
abstract: Here, we explore the mechanism of action of isoxylitone (ISOX), a molecule discovered in the plant Delphinium denudatum, which has been shown to have anticonvulsant properties. Patch-clamp electrophysiology assayed the activity of ISOX on voltage-gated sodium channels (VGSCs) in both cultured neurons and brain slices isolated from controls and rats with experimental epilepsy(kindling model). Quantitative transcription polymerase chain reaction (qRT-PCR) (QPCR) assessed brain-derived neurotrophic factor (BDNF) mRNA expression in kindled rats, and kindled rats treated with ISOX. ISOX suppressed sodium current (I(Na)) showing an IC50 value of 185 nM in cultured neurons. ISOX significantly slowed the recovery from inactivation (ISOX τ = 18.7 ms; Control τ = 9.4 ms; p < 0.001). ISOX also enhanced the development of inactivation by shifting the Boltzmann curve to more hyperpolarized potentials by -11.2 mV (p < 0.05). In naive and electrically kindled cortical neurons, the IC50 for sodium current block was identical to that found in cultured neurons. ISOX prevented kindled stage 5 seizures and decreased the enhanced BDNF mRNA expression that is normally associated with kindling (p < 0.05). Overall, our data show that ISOX is a potent inhibitor of VGSCs that stabilizes steady-state inactivation while slowing recovery and enhancing inactivation development. Like many other sodium channel blocker anti-epileptic drugs, the suppression of BDNF mRNA expression that usually occurs with kindling is likely a secondary outcome that nevertheless would suppress epileptogenesis. These data show a new class of anti-seizure compound that inhibits sodium channel function and prevents the development of epileptic seizures.
authors.affiliation: H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan.
authors.forename: Muhammad N
authors.initials: MN
authors.lastname: Ashraf
authors.forename: Cezar
authors.initials: C
authors.lastname: Gavrilovici
authors.forename: Syed U Ali
authors.initials: SU
authors.lastname: Shah
authors.forename: Farzana
authors.initials: F
authors.lastname: Shaheen
authors.forename: Muhammad I
authors.initials: MI
authors.lastname: Choudhary
authors.forename: Atta-ur
authors.initials: AU
authors.lastname: Rahman
authors.forename: Margaret
authors.initials: M
authors.lastname: Fahnestock
authors.forename: Shabana U
authors.initials: SU
authors.lastname: Simjee
authors.forename: Michael O
authors.initials: MO
authors.lastname: Poulter
mesh_terms: D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D019208:Brain-Derived Neurotrophic Factor / Q000096:biosynthesis / Q000235:genetics; D002478:Cells, Cultured; D053138:Cyclohexenes / Q000737:chemistry / Q000494:pharmacology*; D031882:Delphinium / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004567:Electrodes, Implanted; D055724:Electrophysiological Phenomena; D007536:Isomerism; D007659:Ketones / Q000737:chemistry / Q000494:pharmacology*; D007696:Kindling, Neurologic / Q000187:drug effects*; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D012640:Seizures / Q000503:physiopathology / Q000517:prevention & control*; D015222:Sodium Channels / Q000187:drug effects*
chemical_list: C579616:1,3,5,5-trimethyl-2-cyclohexen-1-ylidine-2-propanone; D000927:Anticonvulsants; D019208:Brain-Derived Neurotrophic Factor; D053138:Cyclohexenes; D007659:Ketones; D012333:RNA, Messenger; D015222:Sodium Channels
keywords: Isoxylitones [E/Z]; brain-derived neurotrophic factor; electrophysiology; steady-state inactivation